Updated July 4, 2023

Introduction to Regression Testing

In a software application, when new changes are made in the existing system or a new feature is added to the application, it is essential to test the application modules that are impacted by this new requirement. This type of testing is known as this type of testing, Regression Testing. For this testing, there are no new test cases designed. Instead, a cluster of test cases is picked from the prior test execution, which is applicable for testing the affected application modules. Most of the time, this is carried out using an Automation Testing tool.

When does Regression Testing Occur?

It is required to do when there is any performance issue, and it has been fixed. There is defect fixing or bug fix, change in requirement, modification of code, and newly added feature to the product or software. The regression testing has to be done for the last-minute deployments and changes done to software or application in production or any other environment.

The test cases are mainly selected on the basis:

The feathe client frequently uses the client.
The core features of the product like new, edit, and view.
The test case, which has logged the defects more frequently.
All types of cases like a boundary test case, integration test case, and complex test case.
The functionalities on which the changes are done or bug has been fixed.
All types of successful test case and failed test cases.

Features

The features of the regression testing are as below:

It helps in saving a lot of effort and time.
It helps run multiple tests simultaneously and maintains the test coverage of previous test cases.
The regression testing is mainly effective on the basis of test cases defined to test the existing functionality or features.
It also depends on the area of impact of the release and the criticality of a component.
The regression test cases are mainly automated, which saves time and effort for a tester, as there are lots of test cases, and manually it can be time-consuming.

Techniques for Regression Testing:

There are various techniques mentioned below:

1. Retest All

It means that all the test cases are executed again that were previously written to make sure that everything works fine, and there are no bugs introduced because of change and a new feature in code. It is one of the most expensive methods because it requires a lot of effort and time, and resources to execute all the tests.

2. Regression Test Selection

In this type of testing, test cases have been selected that need to be executed for testing. All the test cases won’t run for this method; only selected test cases are used to run. These test cases are selected on the basis of code change. These test cases are mainly categorized as reusable test cases and obsolete test cases. Regression test cases are used in succeeding regression cycles, and obsolete test cases can’t be used in succeeding cycles.

3. Prioritization of Test Cases

Test cases that are on high priority can be executed first than others. The medium and low priority test cases are getting executed later after high priority test cases execution. Priority depends on the criticality and impact, and functionality of the product.

4. Hybrid

It is a combination of regression test selection and prioritization of test cases. The test cases are executed depending on priority, and selected test cases will be executed for occurred changes.

Types of Regression Testing:

There are different types of regression testing mentioned below:

Unit Regression: It is mainly executed during unit testing. In this, the code is tested via regression cases as all the dependencies are blocked to make sure that unit testing is done without any discrepancy
Partial Regression: It is mainly executed to verify that code works fine after doing changes in code and that code is integrated with existing code or the unchanged modules
Complete Regression: It is mainly executed when there are a lot of changes in code and in the number of modules. The test cases are executed on the whole software, as there are a lot of code changes.

Planning of Regression Testing

The test plan for regression testing is done to approach the testing of software or application. The new features or functionality implemented, code changes or bug fix and to test the impact of changes to existing code, the regression testing is done through automated test cases. The main idea behind the regression testing plan is to check and know how the testing would be done to acquire the test results. It is done to make sure the features of the product remain unaffected.

The regression testing strategy used to share the approach to perform testing that includes testing technique needs to use, completion criteria usage, writing test scripts, and the automation tool that is being used for covering the test cases. The test cases are executed on the basis of the technology that is being used. It defines the features/components that need to be tested. The test cases are purely based on the project requirements.

Perform Regression Testing

It can be performed in two ways manually and automatically. If it is done manually, then it will take a lot of time and effort; the testing can be done manually till there is less functionality or a small application. The application functionality goes on increasing as time goes on, and it increases the regression scope. To save effort and time, the automation tool is mainly used to test the regression and application existing code.

There are some steps involved in performing the regression testing to execute the test cases:

To conduct the regression testing, the test suite needs to be prepared.
The test cases need to be automated.
The regression testing and its test cases need to be updated whenever there is a new defect found. If the existing test cases are not covering the defects and changes that are done, so the new test case needs to be updated to cover those functionalities.
The regression testing has to be executed even there is a very small change or issue fix. The existing code needs to be tested properly.
The report has to be created that includes the pass or fail test cases after its execution.
The testing time of the application increases as the application development or functionality increases.
For the new version and release of the software release, the tester needs to test and understand the requirement of the change of software that needs to be done.
The analysis of the impact of changes on existing features and modules.
Select the test cases and determine what technique of regression testing needs to adopt.
The testing needs to be scheduled for a particular time and test it.

The regression testing takes more time and effort if the size of the application or software increases, and with new releases, it has to be done completely that will increase the testing cost, but the client generally not ready to pay for testing. The regression testing needs to be reduced, but that cannot be done. Even the regression testing time cannot be reduced, as it is the main requirement to test the application thoroughly. The automation test cases and writing automation test scripts need a lot of effort, and people do need a lot of knowledge to complete the testing.

Testing Tools

The testing tools are used to automate the testing efforts and can be run automatically after code push and build. The test cases available and running them manually will take a lot of effort and time. To reduce the effort and time, automation tools are being used. The test cases are mostly recorded, and playback type only.

There is some testing automation tool available mentioned below:

Selenium
QTP (Quick test professional)
RFT (Rational Functional Testing)
vTest

There are many other tools that are being used for writing scripts and testing the application or software, and test cases are frequently due to change in the system. The testing tool helps in testing the application in some particular ways as well. If there is new functionality embedded or any code change done for the defined period of time or days or in the latest sprint, then test cases need to be executed as per the new functionality added. The other way for executing the regression test cases has to be executed again for all the application modules, and it is referred to as end-to-end regression testing to cover all the functionalities of the product.

Advantages and Disadvantages

Below are the advantages and disadvantages mentioned:

Advantages:

It ensures the existing functionality is working fine and does not affect any part of the software as well.
Regression test really helps in performance optimization.
It helps in implementing continuous integration; as soon as the developer pushes the code, the build is triggered, and the regression test runs automatically.
It helps in improving the quality of the product.
It can be done using automation tools.
It also helps in making sure the same defects should not occur again.
It does not allow doing the new changes while the regression testing is on.
It can be done for databases, and the database needs to be isolated to test. There should be no changes in the database while doing the regression testing.

Disadvantages:

If automation tools were not being used for regression testing in the project, then it would be a time-consuming process.
Manually it takes a lot of effort and time, and it becomes a tedious process.
It has to be done for a small change in the code as it can create issues in software.
Regression testing needs to be done each and every time.
As the test cases become large, sometimes all the test cases cannot be executed because of time and budget issues.
Achieve the maximum test coverage with fewer test cases is always difficult to achieve.
After every release and build of bug fixes, it’s difficult to determine the frequency of regression tests.

Conclusion

It is one of the important parts of testing that helps in delivering a quality product. It makes sure that if there is any change in the code, it won’t affect any existing code or the functionality. It is mainly done through the automation tools only manually; it will take a lot of time and effort to complete. The tool is mainly selected based on the requirement of the project, and the tool should have the ability to update the test cases as well. It helps in getting the defects when new changes are integrated with the existing system and mainly the impact of the changes on different old modules that are not being changed. It is the most important aspect of the testing. Regression testing can be done with the scriptless automation-testing tool; in this, there is no requirement for writing long test scripts.

Regression testing is mainly done through reusable test cases, which are defined as methodology reusability. It generally records and plays back the test case. The testing tool has to make sure that each and every action needs to be recorded properly. There are other ways of doing regression testing as well. Each organization or individual uses the testing as per the project requirement and client budget only.

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